Illuminating DRL and Turn Lights with Single Common Lamp

The article discusses a simple circuit for enabling the turn signal lamp of any car to carry out a two-way function of DRL lights as well as well the stipulated turn lights. The idea was requested by Mr. Artem.

The Request

Hi, Swagatam!

Thank you for your fanaticism with electronics, this is really noticeable through your blog. I've been experimenting with some of your circuits, and everything is okay for now.

Here I kindly ask your professional advise on my project.

Some tiny vehicles have a certain lack of room to place LED lights in order to look fine. For one of those, Nissan Micra i was asked to combine LED Turns and DRL lights without placing one next to another..

Considering a small city car ergonomics i searched the market.

I ordered twin color Y+W 1Watt 350mA LED-Emitters from China, so I could combine both functions by means of some kind a controller at one spot.

And as it often happens, seller did not provide any specs for his product.

4-pin LEDs actually have common "+" so i can not drive six of them in series or implement any known driver. Please advise something useful, I believe you are able to.

Thanks in advance,

Illuminating DRL and Turn Lights with Common LEDs

The Design

The proposed circuit which combines and enables illuminating DRL and turn signal lamps through a single common lamp can be seen above.

The circuit basically allows the same lamp (preferably LEDs) to implement a dual function of DRL lights as well as turn signals, depending on which one is switched ON.

The DRL switch is supposed to be switched ON permanently, so that the connected lamp illuminates through the TIP122 transistor, and as soon as the turn signal flasher is switched ON, the TIP122 is instantly disabled through the BC547, allowing the turn signal to flash the LED at the given frequency.

The above happens since the BC547 becomes triggered ON through the turn signal switching and keeps the TIP122 base grounded and disabled.

The 100uF/25 plays a crucial role here, and makes sure that the BC547 stays disabled for both the ON and the OFF periods of the turn signal inputs, therefore this capacitor might require some tweaking until the right minimum timing is determined.

Bigger values will work but this might result in a delayed switch ON of the DRL each time the turn signal is deactivated, therefore the 100uF value could need some adjustments.

The 10k preset at the base of the TIP122 may be used for determining the brightness level on the DRL, so this becomes an added feature in the design.

Feedback from Mr. Artem

Thank you for the circuit. But it seems  you get me a little wrong. I
wanted the circuit to drive 350ma double color leds, which has single
common "+"positive and two "-"negative pins for white and yellow
respectively. Both chrystalls are in single body for ergonomical
Your suggested circuit doing the job well but we must take two colors with common positive pin in account.

As per the above response, the earlier diagram can be modified as shown below for executing the new function.

I have assumed the LEDs to be having the current limiting feature originally, therefore it's not been shown here or included in the proposed designs. Otherwise 5 ohm, 2 watt resistors cold be included in series with the respective negative lines of the LED module.



8 thoughts on “Illuminating DRL and Turn Lights with Single Common Lamp

  1. Have questions? Please feel free to post them through comments! Comments will be moderated and solved ASAP.
  2. hi. can you suggest a circuit diagram for dusk to dawn control. i have manages to replicate the ones that are used in automatic night lamps which illuminate a couple of led's. Do you have any schematics which can drive regular incandescent bulbs, without using a relay.

    You response will be highly appreciated.

    I have had a sweep through your blog. Your hard work and inputs are admirable..
    Hats off to you. Keep the good work going.

    Linus Fernandes
    9004805177 / 8698303609 / 9321279202

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